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What is the ceiling to prohibited space P-47 (or any other P-zone)?
On the Dallas-Fort Worth sectional, notice one of the few permanently Prohibited airspace zones west of the Mississippi; P-47, around the PanTex nuclear plant in Amarillo, just northwest of Husband Intl (AMA) and within the outer cylinder of its Class C space.
Now, that zone is directly in the path of AMA's longer runway, 4/22, and Victor routes including V12-280 extend directly away from the PNH VORTAC at AMA right over the top of it.
That leads me to think that either P-47 has a ceiling above which airliners are allowed to operate, or else AMA Approach and Fort Worth Center via Amarillo RCO have a dickens of a time routing incoming traffic when the winds indicate use of runway 4/22. The outer Charlie cylinder begins at 4800 feet, but the chart also clearly states that P-47 is excluded from AMA's class C space where they overlap. That leads me to think that this P-space extends to Jupiter, and all flight traffic including AMA arrivals/departures (it's not a big town, but it's not exactly BFE either in part because of Pantex) have to maneuver specifically to avoid P-47.
So, to confirm, is there any altitude at which you can overfly P-47, or in more general terms any P-zone?
It seems kind of silly for many P-zones, including this one, to extend all the way to space, as beyond a certain altitude if nothing else it becomes impractical to dive straight down into the facility under protection. But, if that's the law...

Special Use Airspace is defined by boundaries in all three dimensions1. The horizontal boundaries are depicted on the chart as you describe. The vertical boundaries are in the sidebar of the chart:

You can see here that P-47 exists from the surface (because there's nothing before the "TO") up to 4800 MSL. KAMA is at at 3607 MSL, so P-47 ends 1200' above the airport surface. At a little more than 5 NM away from the airport (measuring on the sectional), that's about 240 ft/NM climb: well within the performance capabilities of almost every powered aircraft. Overflights on the victor airway obviously have no problem at all.
This is used for allowing traffic where it might otherwise not be possible: Consider P-40 and R-4009, above Camp David in Maryland. When the President is not in residence, R-4009 lies exactly on top of P-40. P-40, from the surface to 5,000, is a no-fly zone. R-4009, from 5,000 to 12,500, can be transited with ATC permission.
(1)There's always an exception: see R-2933, over Cape Canaveral: 5,000 to UNLIMITED.

Can you give the link for the chart?

It's part of the Dallas VFR sectional chart, you can get them here: https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/vfr/. The information on the third dimension of the SUA zones on the sectional is toward the lower left, I see it now.

haha, yeah, there's a pretty good reason for the lack of a ceiling on the TFRs at KSC and the Cape. I expect the same is true at Wallops and Vandenberg during launches.


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Can you fly an airliner without an ATPL?
The "captain in the right-hand seat" discussion got me thinking. As of 2013, you need an ATPL to operate any plane operating under Part 121 (as part of an "airline"). Both Captain and FO need this level of license, and new Captains require at least 1000 hours as FO.
However, all you'd need to fly the same model of plane for hire in any other situation is a CPL and the applicable type rating for the aircraft. Prior to 2013 that was all you needed to be hired as an FO on an airliner and get yoke time towards your ATPL and the left-hand seat.
The question is, are there still opportunities for a civilian CPL holder to fly large turbofan-powered airframes for a living on his way to an ATPL? My first thought was freight, but cargo planes for FedEx or UPS operate under Part 121, same as American Airlines. The only thing that really leaves is charter flights, which operate under Part 135 and thus may not require the same stricter regs as a pilot on a scheduled service. But, I don't know how many charter operations are using anything bigger than a narrow-body.

Are you sure you need an ATPL to operate Part 121? I thought requirements for FO was 1500 total

@Radu094 pretty sure; the 1500 hour requirement is for the ATPL.

You don't have to be an ATP to fly an airliner. In fact, you can fly an airliner as a private pilot. John Travolta is the best example I can think of... He has a house right by a private airport and flies his own personal Boeing 707 (with Qantas livery) and another jet aircraft (Gulfstream I think). With any large aircraft like this over 12500 lbs or with turbojet engine(s), a pilot does need a type specific rating to fly such an aircraft as well as needing to be "current" in that type, but may do so as long as current at any certificate "level" of private pilot or above. However, to fly an airliner as a scheduled air carrier pilot, then yes, an ATP is required as this type of flight would not fall under part 91 or part 135 of the FARs, but instead part 121 which requires that all pilots have ATP certificates.

So I guess to follow up, you pretty much have to be independently wealthy to do such a thing as you're talking about. The only exception I can think of is a fire fighting tanker or something like that.

one of my personal aviation sayings is "I would absolutely love to have a jet to fly... as long as someone else is paying the fuel bills."

Yeah, this is a good answer but I was thinking more along the lines of someone who wants to fly planes for a living, not someone with enough money to fly their own personal Boeing airliners as a hobby.

Like I said, the only thing I can even think of would be a tanker for fire fighting. That or join the armed forces. :-)

Is somebody who has only trained to the Private PTS allowed to fly in RVSM airspace?

@pericynthion no, you need at minimum an instrument rating to be up in the flight levels and the aircraft must be equipped and certified for RVSM ops (very accurate instrument certifications for altimeters, and also dual altimeters). Just from the altitudes - FL290 to FL410 - you'll like be needing a high performance and high altitude endorsement as well.

@Pugz good point, though I was wondering whether the higher Commercial / ATPL standards for holding altitude etc were relevant.  I guess not, because you're on autopilot up there anyway.

@pericynthion they're very relevant... planes are only separated by 1000 ft vertically and it is imperative that altitude is held within tight tolerances because the higher you get the more prone to error altimeters are. A pilot must be as or more capable than the autopilot of controlling the airplane by hand should automation fail. That said, if you buy a turboprop or jet, nothing is stopping you as a private pilot from going there if you're appropriately rated and the plane is legal for the operation. You also need an RVSM operational approval as I understand it... forgot to mention that one

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How does the efficiency of a turbofan compare between take off speeds and optimal conditions?
I know turbofans are less efficient than propellers due to accelerating a smaller mass of air faster. So my question here is not comparing turbofans vs other engines, but compare how inefficient is a turbofan operating at take off and low speeds compared to that same turbofan in its optimal conditions?
In other words, how much is the efficiency loss? Are we talking about 5% or about 50%?
Also, why exactly that loss of efficiency happen (again, compared to the same engine at optimal cruise conditions)? Is it just the speed differential between the exhaust and aircraft airspeed, or is it something to do with the compressor/turbine efficiency?

Can you define how you quantify efficiency in this context? Fuel efficiency? Thrust generated per lb of fuel per hour?

Yes, thrust per unit weight (or volume) of fuel

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How will aiport operations at KOAK be affected when taxiway W is promoted to a runway?
For the record, my question is not about mistakenly using a taxiway as a runway.
I've noticed recent changes to the sectional and TAC VFR maps around Metropolitan Oakland International Airport (OAK/KOAK) - it appears that Taxiway W is being "promoted" to a runway close to, and parallel to, Runway 12/30.
Based on the airport map (PDF) and confirmed by the Google Earth image below, aircraft departing and landing on 12/30 (presumably soon-to-be 12R/30L) will have to taxi up or down this new runway.  From the looks of it, this runway will just be marginally long enough (about 7200 ft / 2195 m) to handle short-range commercial operations; certainly the longer runway will still need to be used.
This then begs the question:  How would airport operations be affected if both runways were active?

From Google Earth and Skyvector.com

Your link to the airport diagram was via IP Address (155.178.201.160), which is risky, because we have no idea what site we're visiting (even though it is likely an FAA site).  I changed your link to the well known SkyVector site.

This happened in September 2017, and was only temporary while they closed the main runway for repaving. They did the same thing in 2001. The problem is OAK only has one runway long enough for widebodies/international flights, so shutting it down isn't an option.

@user71659 that sounds like an answer.

@abelenky: I only linked what the airnav.com site had, but thank you for fixing this.

@PeterGreen I was expecting the answer to be something like the runways are too close for simultaneous operations, and FAA standards require Part 139 runways to have parallel taxiways.

@abelenky Please tell the FAA that that's risky. They've been doing it for many years and show no sign of stopping.


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Which book should I study to learning flying in Australia?
I'm interested in buying a text book about learning to fly so that I'll have some basic knowledge when I begin lessons.
Someone recommended the Airplane Flying Handbook (FAA), but I was wondering if there's an equivalent Australian text and whether it's worth getting?

Flying an airplane is same in every country since airplanes don't care about countries. The difference lies in the regulations. For books, at a look at this answer which lists several great resources.

My flying school as recommended the RPL Study Guide by Bob Tait as the introductory text. It covers basic aviation plus Australian (CASA) regulations.

CASA (the Civil Aviation Safety Authority) has a number of resources that might be of interest, in fact a lot of their safety publications and videos are as good as (or better than) the FAA equivalents. As best I can tell they don't have anything equivalent to the textbook-level Airplane Flying Handbook or Instrument Procedures Handbook from the FAA though.
You can find references to the FAA handbooks in some of CASA's CAAPs - for example, the Night VFR Rating information references the Airplane Flying Handbook's section on Night Operations) - so clearly they consider at least some of the information broadly transferrable.
Like Farhan mentioned the operating principles, maneuvers, etc. are going to be largely the same because the plane doesn't care what country it's in. It's the specific regulations (and regulatory citations), airspace design specifics, etc. that will vary but if you're aware of that you can easily pick out the parts that you should pay attention to versus the parts you'll need to go and cross-check in an appropriate Australian reference like the Part 61 Manual of Standards for flight training / practical test requirements.

Thanks @voretaq7. Seems like the CASA site has some really good resources, and I'll go ahead a grab a copy of the Airplane Flying Handbook.

Besides the regulations, the other thing(s) which would be different for you would be related to weather, e.g. Coriolis effect.

CASA (the Civil Aviation Safety Authority) have a number of training publications but they are largely oriented at existing pilots, be they recreational or commercial. For someone interested in becoming a pilot, probably the single most useful CASA publication (other than the regulations themselves) is the Visual Flight Rules Guide which gives an overview of key VFR matters and practices. A lot of the information is also provided at http://vfrg.casa.gov.au/ which is worth a look for the wannabe pilot.
AirServices also publishes charts and supplemental material and it is almost certainly worthwhile getting a VTC chart to become familiar with the area in which you will do your flight training.
However, whether you plan to get a Recreational Pilot Licence or a Private Pilot Licence, the goto book is the RPL Study Guide by Bob Tait. As shown, it comes with a supplement for recent changes. Later books cover the more extensive knowledge required by the PPL and CPL but the RPL is the first step.

The book unfortunately is not cheap but it covers a lot of material in the nearly 400 pages within and there is certainly a lot for the student pilot to get into. It incorporates Q&A at the end of each chapter so you can self-study your way through quite a lot of it.
I did my original training for my FAA PPL with what was the bible at the time - the Jeppesen-Sanderson Private Pilot Manual

Comparing that to the Bob Tait book is interesting and IMHO the Bob Tait content is probably more readable as it doesn't present as simply a technical treatise and it is laced with some very good analogies. For example, apparent wind is presented with pictures of a motorcycle rider which makes it instantly obvious to anyone who has ridden a motorcycle. And the descriptions of moment, force and arm are easier to digest than I have seen elsewhere.
It also uses metric measurements/hectopascals and references what measurement systems the US uses, whereas an FAA-oriented book will never use a metric reference and pressure will be in inches of mercury. And of course a US book will reference US geographic locations & meteorology whereas an Australia book will reference Australian locations and met.
So buy the book for the county where you are training. That said, the used Jeppesen books are less than $10 on Amazon so you might want to pick one up as a supplemental reference.
Update
With CASA blurring the lines between the RPL and the PPL, the RPL Study Guide has now been renamed to  RPL/PPL Study Guide - Volume 1 (The PPL Study Guide is now the RPL/PPL Study Guide - Volume 2).


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What does the Emergency Avionics switch do?
In almost every light aircraft I've ever flown, I recall their being a rocker switch marked "Emergency Avionics". Here's an example:

It's never really occurred to me to ask an instructor/owner what it does nor when to use it. Can somebody here explain what it does exactly?
Also, it appears to always be an aftermarket addition (the switch never quite matches the rest of the panel), could there perhaps be a reason why this second avionics master was added?

My light aircraft doesn't have a switch like that...

I have no such switch in my plane.  I do however have 2 Avionics Master switches wired in parallel, either will power up the Avionics power buss.  They were installed in place of an Avionics Master relay (which was removed) that could potentially fail closed and let high, spikey voltage from the alternator onto the buss during startup (or engine shutdown) and damage the avionics. I turn one of them on after the engine is started, and back off before the engine is shut down.

In what type of aircraft was this picture taken? Between aircraft with avionics from steam to Garmin, Avidyne, and Dynon, this is the first time I’ve seen an “Emergency Avionics” switch.

@DeanF. This is a PA28, and I've certainly seen it in other PA28's. Don't recall seeing one in C150152/172's but haven't flown one in a number of years.

I Have flown various Archers, Cherokees, and Warriors. I wonder if this was specific to a certain run of model years. Any clue?

Doubt it. This one's a late 90's model, Ive flown various older ones and seen it thoughout. I'm almost certain this switch is aftermarket, as they never seem to match the rest of the switches. I wonder if it was a change that was rolled out across the entire range for some reason.

I just pulled up pictures of the panels of club Pipers I’ve rented. Just in case I overlooked or forgot about this switch. None of them have it. That makes me kind of curious what AD or SB prompted this. And, if I need to make the clubs aware.

Check the AFM for that aircraft.  It should be listed there.

Ok. So, I searched through the AFM for the PA28-(150, 160, & 180), revised May 10, 1977, and the POHs for the PA28-181, revised January 05, 2004, and revised May 07, 2018. None of the three had an Emergency Avionics switch on the panel nor in the electrical system diagrams. Poster Fiddlesticks posted a diagram for a PA28-236 Dakota that does have it. Besides the O-540 engine, does anyone know the differences that would warrant the additional switch?

Well, this may not be an answer. Rather, it’s a supposition or a theory. Since the Dakota POH says that the Master switch and the Alternator switch are mechanically interlocked, the Emergency Avionics switch may be the back-up if you have to disengage the alternator. Turning off the Alternator would also switch off the Master. My question is if it is a Off/On switch like it says? Or, is it an Off/Armed Switch like it is with more recently built Essentials Busses and stand-by/emergency batteries? The On/Off variety would require the pilot to actively select it in the case of electrical problems

I've flown a good handful of light airplane makes and models and none have a switch like you describe.

@quietflyer - Yes, I thought the same thing. I’ve flown quite a few G500 & G1000 aircraft with an Off/Armed switch for the standby battery/avionics systems. I had never seen an Off/On switch for Emergency Avionics in what appears to be a steam gauge panel. Yet, Fiddlesticks has found a legitimate reference showing it in the Dakota. I would love to know the official reasoning behind this switch. Especially since the referenced diagram does not have an additional power source represented. Any ideas?

A quick google will turn up some answers. The consensus seems to be that it is just another switch in parallel with the Avionics Master Switch, such that, if the master switch fails, the "emergency" switch can be used to connect the juice instead! The point being that the master switch is a single  point of failure for the entire avionics suite (radios, transponder and nav) - if that switch fails in flight, you lose everything!
EDIT:
From the Piper Dakota (PA-28-236) Maintenance Manual:

Electrical power for various avionics components is controlled by an avionics master switch located near
  the top of the instrument panel between radio stacks. It controls power to all radios through the aircraft master
  switch.
An emergency bus switch is provided to supply auxiliary power to avionics bus in event of a radio master
  switch circuit failure. The emergency bus switch is located behind lower right shin guard, to left of the circuit
  breaker panel.

This is largely unfounded and likely incorrect (insofar as this serves as the backup for the master avionics switch as a component).

The Dakota POH you referenced says that the Master and Alternator switches are mechanically interlocked. Could the Emergency Avionics switch be in case you have to disengage the alternator due to excessive amps or voltage? In which case, you would still be able to manually select battery power to the avionics when the Alternator/Master combo switch were turned off.

I have not encountered this personally myself, but a Google search indicates that the emergency avionics switch is usually used in setup where a relay is used to control the power to the avionics bus.  If the relay were to fail the emergency avionics switch would bypass it.  Relays allow the reduction of high current wiring having to run to the panel with a high current switch.  Instead the switch is a low power switch which drives a relay which would be located closer to the actual avionics bus so not as much wiring would be needed.  More high current wiring increases the risk of hazardous electrical shorts and electrical fires, however mechanical relays do fail eventually.  So the emergency avionics power switch will bypass the mechanical relay in case it fails.

That seems to be self-defeating. You have to run the high-current wire to the emergency switch anyway, so all that does is add one low-current wire.

@HiddenWindshield:  I agree which I think is why most planes don't have this configuration.  There are places where a relay would make sense, like the starter circuit, but I don't think a relay on the avionics bus makes much sense.

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Piloting as a perishable skill - what skills go first and how to self-assess and mitigate skill loss?
I know that in accident reports they will typically say the total number of hours the pilot had, but also the total hours in type and total hours in the last 90 days.  I know from personal experience that landing an airplane can be a perishable skill (I recently went 60+ days since flying and my landings were not the picture-perfect examples they usually are...don't get me wrong, nothing unsafe, just wasn't proud of them...drifting off centerline, excessive float, etc :)
The FAA seems to know this with the 90-day passenger carrying requirement (3 take-offs and landings within 90 days to carry passengers during the day and 3 to a full-stop for night passenger carriage).
All this to say flying doesn't seem to be "just like riding a bike - you never forget it."  But in what sense?  The muscle memory goes? The "seat of the pants" sensation starts to feel foreign?  I know charts can change, regs can change, but do you really "forget how to fly," or just "lose the touch?"
What skills go first, and what is the best way to self-assess your skill quality and mitigate the loss of it?

I imagine the skills that go first vary depending on the pilot. The instrument scan and the precision required for IFR flight could certainly atrophy pretty quickly, the skills required for "normal VFR cruise flight" would probably be the last to go (keeping the wings level and holding a course is about as easy as it gets - you might not be graceful at it, blowing altitude or overshooting turns - but many pilots had on their first or second lesson and they should come back pretty quickly)

Having not ridden a bike for over 15 years I have to say that riding a bike is not just like riding a bike. I had to relearn how not to fall when I tried teaching my son how to ride a bike.

I have no hard data answers to your questions. Perhaps others will. I can, though, offer some personal observations.
My last two jobs were at 747 carriers. At the first we had two weeks on, two weeks off. At the second, we had 12 days off a month, which, with a little seniority, you could arrange to have as a block.
For me, the first thing to go was my instrument scan, and I used to joke that it took only 4 days of inactivity to lose that. The joking aside, I did notice a slight degradation the first day or two upon returning to work after time off. I should note that my habit was to hand fly the airplane to the first cruise level, and then to hand fly from the top of descent, so I perhaps would notice a bit of degradation more so than those who used the autopilot as soon as possible and until as late as possible.
I retired 15 years ago, and it had been 30 years since I had flown a light single engine airplane when, a few weeks ago, I decided to check out in a Cessna 172. After three sessions, the instructor said he was satisfied. I wasn't and we went out a four time, and he signed me off for my first-ever BFR.
In general, I did a little better than I had expected. In one area, landings, I did a worse. The problem was the sight picture I had in my head from 10 years of landing 747s. On the first landing, knowing that I'd want to flare high, I delayed rounding out until my gut way saying, "if you don't flare, you will crunch the airplane." When I started the flare, the instructor said, "No, you're way too high." I delayed again, then started again, and the instructor said I was still too high." I delayed again, then absolutely had to start again, at which time the instructor said something like, "Well, you're still high but go ahead." That landing was followed by three sessions of nothing but takeoffs and landings. Each session I improved, but, frankly, I have yet to get a really good landing. My next session will be solo and will be nothing but takeoffs and landings.
So, for me at least, I conclude that we don't forget how to fly, but we definite do lose the touch.
After I get the solo takeoff and landings session in, I'm going to go out with the instructor and shoot a couple of ILSs. I'm expecting my instrument scan to be terrible.

Thanks. I know my scan goes quick as well.  What I've found is that I mitigate this a bit using a sim, even something like FSX or X-Plane.  How do you think your cross-country planning and decision-making skills are?

@Canuk Not good. The Garmin GNS 430W in the 172 is totally new to me. For the last 10 years of my career, I used the old Carousel inertial systems that had to physically spin up before use. They put in a small GPS update box for the inertial systems during the last year or so. So far, I've only mastered what's necessary for communication on local flights. Insofar as flight planning is concerned, that was primarily something dispatch did. Captains were consulted only for unusual situations. So, I've a lot of work to do there. I may have to buy an iPad. lol

This is basically my "Well I'm WAAAAAAY not current..." routine -- if you're not sure of your skills go up with an instructor to make sure you're bare-minimum safe. After that you can drill yourself to meet the Practical Test Standards which is a great way to knock off rust. You can always grab an instructor again for anything that you're not able to polish back up to standards.

Did you try to look down sideways before flaring? This has helped me most in judging the actual height and works great in a high wing plane. Only looking ahead does not help, and all it takes is a split-second glance sideways.

@PeterKämpf Oh, yes. In fact after lining up on the runway for the very first takeoff and for a few subsequent takeoffs in later sessions, I paused on the runway to look sideways for a bit and try to get that perspective in mind. I talked to an instructor who had checked out a couple of 737 pilots and she said even they had a bit of a problem with flaring too high at first. I think the problem is one of having to unlearn an internalized reaction in favor of the new situation. Don't know if that last statement really makes sense.

@Terry: I understand the unlearning thing - after having flown ASH-25 and SB-10, I paused a few months, and then the fist glider I flew was a Schweitzer 2-33. I came in VERY low and almost landed short of the field. But what I meant is to look sideways just before you think it is time to flare, at the end of the approach.

It very much depends on the person.  My landings and scan seem to stay pretty well, but I forget how to communicate with ATC, how to run the GPS modes, and I have a much harder time figuring out headings, and I also tend to make very steep approaches to landing (VFR) after not flying for a few months.

The Killing Zone: How & Why Pilots Die by Paul Craig (excellent book) has the results of an FAA study of this question, called Private Pilot Flight Skill Retention 8, 16, and 24 Months Following Certification. This table from the study lists the 27 skills they examined and the percentage of pilots who could perform them to PTS standards:

Based on this data, the first skills to go are accelerated stalls and magnetic compass turns: both were at 51% after 8 months. In some cases it seems obvious why the skill degrades: most pilots rarely - if ever - need to make magnetic compass turns so it isn't surprising that that particular skill goes away quickly. On the other hand, after 2 years only 60% of pilots could take off properly, only 51% could land properly at an uncontrolled airport and only 54% at a controlled one. That's all rather worrying considering that pilots usually take off and land at least once per flight.
As for how to assess and improve these skills, you could systematically work through this list in practice flights (like this guy has been doing in his last couple of videos), and/or get a regular review with an instructor. Just because the FAA requires a review once every 2 years doesn't mean that you have to wait that long: every 12 months or even every 6 may be more useful, especially for new pilots. Additional flight training of any kind will also help you to keep your skills sharp: get an instrument rating, commercial license, tailwheel endorsement, seaplane rating, glider rating, checkout in a new aircraft model etc.
But whatever approach you take, the first step is to critically review your own performance after every flight and make notes about what you did well and what you need to improve. If you don't do that, you have little or no chance of coming up with a good self-improvement plan.

Great information, really, BUT it doesn't consider currency which is what this question is about. Pilots can be very current or way out of currency at the 8/16/24 month points.

@Lnafziger It's true that currency is important but I think the OP mentioned it mainly to make the point that it's well understood that skills degrade, hence the need for legal currency in some cases. However, his basic question is which skills go first and fastest, regardless of formal currency requirements. At least, that's my take on it, hopefully the OP will clarify if I misunderstood.

I guess my point was that this includes people that fly every day as well as those that took the check ride and hung up their hats shortly thereafter.  Some subsets of this group will be current while others are not, and their skills most likely stack up differently, while averaging out to what is in the table.  I wish that we had access to the underlying data along with currency information. It would be interesting to analyze!

@Lnafziger Yes, absolutely! The raw data isn't in the Craig book and I couldn't find a free copy of the original study online. The book is entirely based on an analysis of accident statistics and he spends a lot of time talking about currency and total hours, so there's a lot more information there.

Really interesting.  This is the first time I've actually seen some data on this. I would be interested in knowing if there were any currency qualifiers like @Lnafziger suggests.  However, I thought this comment was interesting "Pilots' ability to predict and evaluate their own skill retention levels for specific flight tasks was negligible."  Maybe it's best to just systematically work on each of these tasks whether you think you need them or not.

Sorry to necro an old question, but looking at this chart, to me it really says that the level of instruction is just not as good as it should be. The high checkride scores followed by a pretty steep drop in performance in some situations shows that CFIs may be teaching to the test rather than teaching people how to fly. When I started my Instrument training, I used the AI and DG only for the first couple of hours. Then the instructor took them away. It was turn indicator and mag compass from there on out. Was it required? No. Did it make me a better all-around pilot? I think so.

And all that said, my primary instructor focused heavily on the fundamentals. Though I think it helped I learned out of a field that was 1900'x25' with trees and cows. Anyway, I've always said that you really teach a person to fly an airplane in the first 10 hours. That's the easy part. Every thing after that is how to handle the bad stuff. Good fundamentals will go a very long way, and any CFI should really pay attention to the above chart.

I agree with @Terry, but to add a couple points. If I go without flying for an extended period, some skills that I am rusty on are:

Emergency Procedures.
Getting the feel of the airplane again.

As far as emergency procedures, if I'm flying everyday I find it beneficial to do a take-off briefing (failed engine before/after lift-off). When I come back from a hiatus of flying, these take-off briefings take a bit to remember and get back in the groove, reaction time is critical. Sometimes I will practice forced-landings when landing at home (when proficient, it's no big deal hitting your mark). When I'm rusty - it's a bit more sloppy.
As far as getting the feel of the airplane again, some things I notice are landing too fast, maintaining coordination takes a bit more work (muscle memory). Basically, just general flying skills.
The best way to mitigate the loss is to fly at least once a week, even if it's just a trip around the pattern, that will help tremendously.

Once a week would be really nice, but doesn't seem terribly realistic for most.  Even when I was in training I was only able to fly about once every other week (between airplane breakages, weather, work, etc).  Now, once a month is a LOT, I'm frequently out of currency just from not being able to get to the airport every 90 days!

@BrianKnoblauch, my personal opinion is if you only fly once a month, you will never be proficient.

“If I don't practice one day, I know it; two days, the critics know it; three days, the public knows it.”
-- Jascha Heifetz

This is a big question to unpack and I don’t know if it has ever been studied.  I would guess this really depends on the pilot in question and their personal strengths and weaknesses in their airmanship.  Some people need constant practice in certain areas to remain proficient where as other skills are not that much of a struggle.
What I’ve found is, with lack of practice the first big thing to go is what I call “being in the groove”, that is being unconsciously competent with all aspects of the operation of the aircraft so I can control it with brain stem flying and leave a lot of my higher cognitive capacity free to handle higher order tasks and unexpected happenings.  If I haven’t flown for a while, I feel like I’m stumbling, getting behind the airplane and really have to concentrate on basic flying tasks like attitude, power settings and coordination in turns.  I can be behind the ball on checklists and ATC work as well.
One of the earliest things to go can be technical proficiency on complex maneuvers, for instance Lazy Eights, Eights On Pylons, etc. that require a lot of control finesse that can only be maintained with constant practice.  Crosswind takeoffs and landings skills, especially in gusty conditions also atrophy quickly.
As Terry points out a lot of proficiency is airframe dependent.  Switching between airframes to one which you have not flown in a while can cause proficiency problem, even if you are current and qualified on another airframe due to the quirks or each type.
Emergency procedures are another area that can really languish if not practiced on a regular basis.  This is especially true of twins that demand a high degree of readiness an proficiency in the event of an engine emergency during takeoff and landing operations.
If you have been out of flying for a period of time the best advice is start easy and work progressively more complex.  You don’t want to just straight into an instrument flight in a new airframe in busy airspace, even if you are current.  But som trips around the pattern first of a good weather day with light winds would be a good warm up.  Also consider making the first flight dual with a flight instructor to get you back up to speed.
As for skill assessments, you can use the ACS guide for your level of pilot certificate as a basic yardstick.  Fly a task listed therein and then review what you did against that standards set there.  Can you meet both the knowledge, risk assessment skills and performance requirements listed?  If not what went wrong and how can you fix it?  Also go up and fly with a CFI or flight examiner and see what they think.
The only way to mitigate the degradation is with constant practice.  There is no other way to stay proficient and current.

"I don’t know if it has ever been studied" from an accident causing perspective at least, it seems that it has been studied - see pondlife's answer.

Well, kind of.  The answer is a kind of metric on some skills but I really don’t see an understanding of the psychology of perishable skills.

its says "aircraft," so I will answer for the categories and ratings I hold:

Airplane Single Engine Land/Sea -- landings
Rotorcraft/helicopter -- autorotations
Gliders -- tow rope breaks
Tailwheel -- wheel landings
Complex + high-performance -- managing cowl flaps, wing flaps, rudder trim, engine cool-down, gear, etc.
High-altitude -- emergency descent to 10,000ft
Instrument/airplane -- partial panel

Having never been in a glider, how often does the tow rope actually break? Is it pretty common?

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Where can I find a collection of maximum range at maximum payload values for all aircraft types?
The scope of my Master Thesis is the development of an assignment algorithm of aircraft types to routes with a given distance. As part of violation checks I'm validating the possible range of the AC type against the route distances.
As defined per payload-range diagram the max range of an aircraft type is not a static value but depends on the amount of payload desired. For a more realistic approach I'm looking for values of the max range at maximum payload of every aircraft type defined in ICAO Doc 8643.
However this value is not very easy to find out. Does anyone have an idea where to find a list of all (or at least all major aircraft types) max ranges at max payload of all aircraft types given in ICAO Doc 8643 grouped by the ICAO Designators (e.g. A332, B773, etc.)

The range is not only depending on aircraft type and payload but on many more variables like winds, temperature, cruise speed, installed engine model, number of installed fuel tanks etc. etc.

I doubt such a list exists. You would likely have to compile the list from each PIM.   Creating new datasets that didn't exist before is a wonderful output from Master Theses.

I always enjoy looking at sales material for new aircraft... They usually have several range rings. As any pilot knows... It can be quite dependent on weather.

One ICAO designator can indicate multiple aircraft types with different MTOW and engines. Take for example the A320 and A320neo, or Boeing 767-300 and 767-300ER (with or without winglets). Instead of looking for every aircraft type, I would suggest to take just a few aircraft types (specify them more detailed) and try to get information for them. This website may help you, but I didn't check how reliable the numbers are.

Hello together! Thx very much for the many replies. I'll have to validate the different recommended sources. Overall I know about the comments of @DeltaLima. The purpose is to get a good average of all these variants of the single AC types

@FelixWindisch If I were you, I wouldn't go for the average of all these variants but instead pick a single variant and explicitly state which one you took. You could for example take the most common variety or the one that has an average performance. That way you avoid fuzziness in your work and increase the value of the results.


text:
What are the rules regarding airlines picking up passengers at stops in foreign countries?
Suppose Air Canada flies from Vancouver to Santiago with a stop in LAX. I am vaguely of the belief that they are not allowed to pickup Americans who wish to travel from LAX to Santiago, but I'm curious to know more about these rules (if they exist). Also, how they apply (or not) internationally, ie. not just in America.

The short answer to your first question is that an airline can pick up passengers at an intermediate stop as long as it's previously been agreed by all the countries involved (see below). One example is Singapore Airlines SQ12, which flies SIN-NRT-LAX; many passengers leave and board the aircraft in Tokyo.
More generally, these rules are known as the freedoms of the air but they aren't consistently or fully implemented everywhere and a lot depends on agreements between individual countries. Your first question is about the fifth freedom:

the right to fly between two foreign countries on a flight originating
  or ending in one's own country

As Wikipedia describes, this isn't always straightforward:

The negotiations for fifth freedom traffic rights can be lengthy
  because in practice the approval of at least three different nations
  is required

If an airline stops in an intermediate country to refuel or for other technical reasons but isn't allowed to board or deplane customers, that would be the second freedom:

the right to refuel or carry out maintenance in a foreign country
  without embarking or disembarking passengers or cargo

There's an interesting discussion of fifth freedom flights from a passenger perspective here, and you may get better answers on this topic on travel.SE.

Another important consideration is each planned OR potential stop for the aircraft (potential meaning a diversion or extra stop for fuel, maintenance, weather or passenger issues such as illness). Any passenger boarding an international flight must have all the appropriate documentation for both entry AND exit for stops even if they are to remain aboard while some other passengers enplane or deplane. The reason is, so that a person is not arrived physically in a destination they have no proper credentials for (EX: a VISA or passport or both)

Aircraft certainly make planned diversions (and even planned fuel stops) in countries where passengers do not have permission or documentation to enter or exit. For instance, a flight from the US to Europe may divert to Canada for a serious medical emergency, even though everyone on board is unlikely to be admissible to Canada. A flight from San Francisco to Hong Kong may make a planned fuel stop in Taipei due to strong headwinds, even though everyone on board doesn't have documentation to enter Taiwan. The requirements will depend on each country's rules of course.


text:
What is the difference between saturated and unsaturated adiabatic lapse rate?
I'm having trouble understanding the difference between saturated and unsaturated adiabatic lapse rate.
I know the unsaturated adiabatic lapse rate is approximately 5.4 degrees per 1,000 feet in which a "dry" parcel of air cools at that rate. What does the unsaturated adiabatic lapse rate depend on? Why is the unsaturated adiabatic lapse rate lower than the saturated lapse rate?
I searched and found that the unsaturated adiabatic lapse rate is lower due to the air parcel releasing its latent heat, which causes the air parcel to cool slower, but I don't get it. When a "dry" parcel of air is cooling adiabatically, are we assuming 0% moisture?

Probably better on Earth Science.SE.

Very related: https://aviation.stackexchange.com/questions/29922/do-thermals-stop-rising-when-clouds-are-formed/ and https://aviation.stackexchange.com/questions/35432/how-can-a-pilot-anticipate-cloud-formation

The difference between a unsaturated and a saturated adiabatic lapse rate is that in the latter the water vapour has to change state from gaseous to liquid.
When air rises it expands due to the lower pressure of the ambient air at higher altitude. By expanding, the air parcel is doing work on its surroundings. Since no heat is transferred to the air parcel (by definition of being adiabatic expansion) but work is being performed, the temperature has to drop. Thus a rising parcel of air cools down.
Cooler air can hold less water vapour than warmer air. If the air parcel contains water vapour, at some point during the cooling the maximum relative humidity is reached. At that point the air is saturated with water vapour. If the air continues to cool, the water vapour content has to change from vapour to liquid. This is called saturated adiabatic cooling.
The process of condensation of the water content is exothermic; when the state changes from gaseous to liquid, heat is released to the air in the parcel. Therefore the lapse rate (temperature change with altitude) of a saturated adiabatic process is less than an unsaturated adiabatic process. The heat released from the condensation process reduces the lapse rate.


text:
What is the relation between a helicopter's length and rotor diameter?
I was looking at a couple of helicopters on Wikipedia (specifically the Boeing A160, the Robinson R22, and the Sikorsky S-46) and I noticed the main rotor diameters seem to be pretty similar to the helicopter length (see below).
Is there a reason for this, or is it just coincidence? I thought it might be that helicopters are just long enough for the tail rotor to not interfere with the main rotor, but that doesn't seem to work out, because the rotors aren't quite centered over the helicopter.

Helicopters' length and main rotor diameter legend:
                Length     Rotor Diameter
Boeing A160      35'0"        36'0"
Robinson R22     28'8"        25'2"
Sikorsky S-64    70'3"        72'0"

Related question

The rotors are centered over the helicopters. They are just centered over the center of gravity, not the geometrical center.

Important.  I am a helicopter pilot, with no expertise or experience in design so I can give you reasons for this, but not design detail.
Most design decisions are compromises.  Helicopter rotors are definitely compromises.
What is the aim of the rotor design?
To have the smallest possible rotor to achieve the performance requirements of the craft.
What limits the smallest size?
Let's assume that the blades are as efficient at generating lift as you can make them.  There are only 2 ways to increase lift for any given blade at any given angle of attack.  That is to increase the length of the blade or to move it faster through the air, i.e. to make the rotor spin faster.
What limits the speed at which the rotor can rotate?
As the blade tip speed gets faster, drag increases with the square of the speed.  Increased drag means increased power required which means heavier engine and heavier gearbox.  As speed moves to a high percentage of supersonic, turbulence and therefore drag increases enormously.  The longer the blade, the lower the possible rotor RPM since the tip approaches supersonic speed more quickly.
Why not just increase the length?
Because the blade becomes increasingly difficult (and expensive) to manufacture to handle the loads on the blade and the heavier they become requiring more robust and heavier rotors hub assemblies.
The inner part of the rotor also produces little lift since it is moving relatively slowly and since lift decreases with the square of the speed, the lift generated falls away rapidly as you move to the inside portion of the disc.  As you increase the length of the blade, without being able to increase the speed of the disc as above, the area of the disc which is "useless", increases as a proportion of the overall disc size.  Therefore, more power is needed to rotate the increasingly large useless area of the disc.
The lower the disc loading, the more efficient the helicopter is in the hover.
The disc loading is the ratio of the weight of the helicopter and the area the rotor disc describes as it rotates.  The disc loading should be as low as possible to reduce the required strength, and thus weight, of the blades especially as the weight of the helicopter increases under positive G which in turn increases the disc loading.
Non-performance considerations.  Parking; hangar space required; ability to operate in confined areas.
Given these (and other design parameters), the rotor sizes you quote will have been arrived at by factoring each of the variables to find the best compromise, according to the designer, between them to achieve the desired performance goals.
Therefore, I don't believe that there is a relationship between the fuselage length and rotor size, possibly with some influence from the need to park and hangar the resulting craft.
[EDIT]
I've been hoping that some better informed answers would be added.  As there are none, I'll continue with my simple pilot guesswork.
What is the aim of the fuselage design?
To have the smallest possible fuselage to achieve the performance requirements of the craft.
What limits the smallest size?
How many crew?  How many PAX?  Level of comfort (utilitarian - R22, or comfortable - Long Ranger).  Fuel load.  Engine and gearbox size.  Cargo and other payload.  Baggage stowage?
What limits the maximum size?
Weight.  Profile drag.  Cost to manufacture.
Non-performance considerations.  Parking; hangar space required.

The bit about retreating blade stall sounds to be reversed. The retreating blade moves aft at own speed minus craft speed and must still move aft to produce lift, so the blade's own speed must be higher than craft speed to produce lift. So higher blade speed allows higher craft speed.

Err hmm, cough cough, er, yes, you're right.  I'll edit.  Thanks.

This gives a lot of great information about how rotor size is determined, but skimps on fuselage length. Obviously that's partially determined by the hangar size and such, but there's also some sort of lower limit, or else we'd see more tail-less helicopters. I guess with a shorter tail the the tail rotor would have to be larger to exert the same torque and effectively counteract the torque from the main rotor?

@raptortech97 I edited in some additional reasoned guesswork.  And you are correct about the length of the tail boom.  Not just the tail rotor but the ability of the boom and fin (if present) to add yaw stability which is also a lever.

next time you do an auto, say to yourself "the center part of the blade is useless" and see if it rings true

@rbp Yes of course, when it becomes the driven region, but under power, it is.

Disclaimer: I am a copter pilot, but not a designer
The rotor generates a certain amount of torque that would swing the body in the opposite direction of the turning rotor (Newton III).
The pedals are called anti-torque pedals, which counteract this behavior, and allow the body of the copter to be yawed independently of the rotor.  In a copter which has either a tail rotor or a ducted fan (rather than two main rotors), the amount of force generated by the tail must be sufficient to allow a 360 degrees of yaw in nearly any regime of flight. Increasing the distance between the main rotor and the tail rotor increases the effectiveness of the anti-torque pedals. A longer tailboom would allow a smaller tail rotor, and require less engine power to be diverted by the transmission, and vice-versa.

If the helicopter has a main rotor and a tail rotor:

The main rotor is attached very near the centre of gravity.
The tail rotor needs as long a moment arm (tail boom) as you can give it, but needs to be balanced weight-wise with the business end of the helicopter, where the pilots sit.
The tail rotor axis is preferably mounted at the same height in the helicopter as the main rotor - outside the main rotor radius of course. This is done to prevent a rolling moment to occur when lateral stick compensates for tail rotor side force is the hover.

So yeah, for that configuration that's what you end up with, roughly similar dimensions for fuselage length and rotor diameter.
Not for this one though: it has two rotors, each one with a diameter 40% wider than the fuselage length. They do have a stubby tail boom to provide directional stability via the vertical tails, otherwise this helo could just be shaped as a laundry tub, really.

Just to add to some prior comments.

Larger main rotors are actually desirable aerodynamically.  They burn less fuel per unit weight lifted.  Main rotors create thrust by throwing air downward, and throwing a larger volume downward at a lower speed (i.e. large rotor diameter) is more efficient than throwing a smaller volume down at a higher speed (smaller rotor).

A smaller main rotor can also carry more weight by increasing the chord length of the blades (in addition to other things mentioned).

Increasing helicopter length gets the tail rotor further aft which makes it more efficient at countering main rotor torque.  A tail rotor twice as far aft can counter twice as much torque with the same tail rotor thrust.  Of course, making the helicopter longer adds weight and hence increases main rotor thrust & torque requirements, so there's a balancing act here.

Regarding the rotor speed comments.  Noise and advancing blade compressability are normally limit the rotor speed.  Blade tips need to stay below Mach 1 for reasonable  aerodynamic loads.


text:
From how far strobe lights are visible?
At what distance would you begin to see the sequenced flashing strobe on an approach light system at night? 10 NM? 20 NM? Visibility plays a role, but consider CAVU.
Also, strobe lights on radio and cell towers, what is their visibility distance at night?
And at those distances, are they initially faint as they fade into view?

Isn't that the visibility part of a weather statement, i.e. visibility 5 miles means you can start to see the identification lights at 5 miles?

requirements that I found all mention only candelas required (in the order of 270k in the day and 2k during the night)

also relevant wiki page (no refs though)

I think you are assuming that the airplane is approaching the lights at the optimum angle.  In fact, the approach lights are highly directional.  While a passenger in a GA plane, we crossed the final approach path to runway 6 at KISP (a Class C airport) and the lights went from not visible, to visible, to not visible  in a very short time.  So even though you know the optimal visibility, remember that it may be a lot less or zero if you are not in the best spot...

@CGCampbell: I believe only runway visual range (RVR) is defined that way. And it is often larger than reported visibility.

For cell towers the FAA wants them to be visible for pilots in time for them to avoid them.

Pilots of aircraft travelling at 165 knots (190 mph/306kph) or less
  should be able to see obstruction lights in sufficient time to avoid
  the structure by at least 2,000 feet (610m) horizontally under all
  conditions of operation, provided the pilot is operating in accordance
  with FAR Part 91. Pilots operating between 165 knots (190 mph/303
  km/h) and 250 knots (288 mph/463 kph) should be able to see the
  obstruction lights unless the weather deteriorates to 3 statute miles
  (4.8 kilometers) visibility at night, during which time period 2,000
  candelas would be required to see the lights at 1.2 statute miles
  (1.9km). A higher intensity, with 3 statute miles (4.8 kilometers)
  visibility at night, could generate a residential annoyance factor. In
  addition, aircraft in these speed ranges can normally be expected to
  operate under instrument flight rules (IFR) at night when the
  visibility is 1 statute mile (1.6 kilometers).

http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2070%207460-1K.pdf (page 63)

Flying through Central Valley of California at night I have seen runway light from many miles away.  Probably 20nm+.  The valley is low and flat with with a lot of airport in low population areas.  As a result the runway lights in general, and approach lights in particular really stand out.  Conversely when you are in a highly populated area (ex. Southern California) while the light travels as far, but you may have trouble picking up the runway environment out of the sea of lights.  So having slant visibility does not necessarily equate to "seeing" the airport.


text:
Is the Reynold's number a function of the fluid flow stream or the obstruction?
I am slightly confused with this notion of the Reynolds Number. Specifically, I am looking at airfoil performance at very low Reynolds number.
I am reading a lot of papers saying things like because it is a small model aircraft, the Reynolds number will be small (so then it is to do with the shape of the obstruction in the fluid flow?). But then I see something like large turbine performance at low speeds involve low Reynolds numbers (from here I would think it is to do with the 'quality' of the fluid flow itself, whether it is laminar or turbulent, uniform etc).
If it has something to do with the fluid flow, then why do I see Reynolds numbers attributed to specific airfoils etc? Say that an airfoil has $Re=100000$, what does this mean then? If the fluid is flowing at a very low speed with high viscosity, then how can we make use of this number at all?
Do correct me if I'm wrong, I am only beginning to learn these things!

This answer explains what affects the Reynold's number. Basically speed, size of obstruction, and gas properties.

One nice thing about Reynolds number is it is dimensionless. So you could test a big wing in air at high speed by using a smaller wing in water at lower speed and if the Reynolds number is the same it gives the same results.

Maybe it helps to see the Reynolds number as the ratio of inertial to viscous forces. High flow speeds mean high inertial forces, and so lead to high Reynolds numbers. Viscous effects are strongest when the airflow hits the obstacle, and become less strong the longer the air flows around a body, so a short flow path has a low Reynolds number.
In the end it does not matter if the length of the flow or its speed drive the Reynolds number up. It is the combination of both. I am neglecting the gas properties here, because I assume we talk about air at moderate temperature and do not want to make the issue more complex.
Airfoils have no Reynolds number per se, flow conditions have. The Reynolds number of a measurement can be doubled by making the chord of the airfoil twice as long at the same airspeed, or by doubling the airspeed at the same chord. The wing of an airplane operates in a range of Reynolds numbers, depending on flight speed. That is why polar diagrams normally contain the results of several test runs rsp. computations, each at a different Reynolds number.
Sometimes you see airfoils which are optimized for a particular Reynolds number. To avoid early separation, the recompression area of an airfoil must become proportionally longer the smaller the Reynolds number is at which the airfoil is supposed to function well. At higher Reynolds numbers such an airfoil will still work, but will produce more drag than one which is optimized for a higher Reynolds number. The Reynolds number allows the aircraft designer to pick an airfoil that works well at the combination of speed and chord length for which that airplane is designed.

Would I then be right in saying that there is no such single Reynolds number, but rather depending on where in the flow field we are looking at, we get a variety of Reynolds numbers? (If so, then is the quoted Reynolds number some sort of an average value?)

@midnightBlue: Yes and no. If you look at boundary layer phenomena like laminar-to-turbulent transition, a local Reynolds number is useful. If there is no pressure gradient, transition happens around Re = 400,000. But if you compare full airfoils, you need to take the Reynolds number for the full chord, or the comparison is meaningless. The quoted number is always that at full length.

The best way to understand what a Reynold's number means is to look at the formula:
R# = velocity of fluid * characteristic length / kinematic viscosity of the fluid
Velocity = speed through the air,  characteristic length = the length of the airfoil along the chord,  kinematic viscosity = how gooey!) the air is
You can see that the Reynolds number depends on the airfoil shape as well as the conditions under which it is being examined. A higher Reynolds number means you are testing a longer airfoil at a higher speed in "thicker" air, or some subset.
It is useful when trying to predict performance. NASA uses pressurized wind tunnels in certain circumstances to affect viscosity, allowing a small model to better predict the performance of a full size wing.
Here is a calculator you can play around with:
http://airfoiltools.com/calculator/reynoldsnumber


text:
Does 14 CFR 91.146 (Charitable Events) apply if the pilot does not seek compensation or hire?
I'm at a loss between regulations §91.146 (Passenger-carrying flights for the benefit of a charitable, nonprofit, or community event.) and §61.113 (Private pilot privileges and limitations: Pilot in command.)
§91.146 contains language that allows a private pilot (who meets 500 hour requirement, among other items) to operate as PIC for a charitable event. The language emphasizes that if the event doesn't meet the charity requirement, it is to be considered commercial.
Do these restrictions under §91.146 / §61.113(d) apply if a pilot is willing to PIC under the criteria of §61.113(a) and cover all expenses of the flight?

§61.113   Private pilot privileges and limitations: Pilot in command.
(a) Except as provided in paragraphs (b) through (h) of this section,
  no person who holds a private pilot certificate may act as pilot in
  command of an aircraft that is carrying passengers or property for
  compensation or hire; nor may that person, for compensation or hire,
  act as pilot in command of an aircraft.
....
(d) A private pilot may act as pilot in command of a charitable,
  nonprofit, or community event flight described in §91.146, if the
  sponsor and pilot comply with the requirements of §91.146.

It would seem to me that the first of those paragraphs forbids carrying passengers for hire, even if the pilot isn't receiving any payments. The second would seem to be an exception to that, with some restrictions.

Let's look at this from two angles -- first, what's OK under 61.113 (basically "no compensation except the pro-rata sharing of expenses" when acting as a private pilot).
The FAA has an incredibly broad interpretation of "compensation" - The foundational counsel opinion is an interpretation to Joseph A. Kirwan, and if you search counsel opinions for Kirwan you find a bunch of additional opinions referencing it.
Basically Kirwan and the other opinions state that the receipt of anything of value is compensation.
That could include:

Money, obviously.
Free or discount fuel/oil
Free meal
Lodging
Logging of flight time (if you're not responsible for the operating expenses of the aircraft)
The receipt of a benefit (usually money) by the organizer (charity)
(Weybrecht, 2010 - if they get the ride in exchange for a donation or attendance fee it's 91.146)
"Valuable Good Will"
(Again in Weybrecht from above - so yeah, If you fly your buddy somewhere and they "owe you one" that might be a violation.)

There's really almost nothing you can do under 61.113 except fly somewhere for a hundred-dollar hamburger and split the cost of gas (under the FARs you even have to pay your pro rata share of the burger) - it's very restrictive.

Now let's look at 91.146 - like DJClayworth pointed out what this  basically does is carve out a small set of exceptions that allow community groups and charitable organizations which have friendly pilots to offer "airplane rides" in exchange for a donation without being in violation of the FARs (risking the friendly pilot's certificate, and the possible wrath of the FAA on the organizer).
There are lots of restrictions (Like the 500 hour requirement, the requirement that flights be "Nonstop, beginning and ending at the same airport, and within 25 miles of the airport of origin", the limit of reimbursement for the pilot being "pro rata share of expenses", and notification of the local FSDO).
The FAA wants to basically make sure pilots are not flying tons of these charity flights every year to basically build time, and that charities aren't operating de facto air tour companies under the exemptions of 91.146.

So what's the answer to your question?
Basically If the organization is getting donations/admission fees/raffle proceeds, etc. in exchange for these flights the operation falls under 91.146 (because the charity is receiving compensation -- the donation).

Great reference with Weybrecht, 2010!

@AndyLevesque Yeah, that seems to be the most directly applicable to your question. There are others that turned up in the search (link now fixed) that make for interesting reading too.

This basically boils down to whether or not anybody is receiving compensation, not just the pilot.
If you are just giving people a ride, with no payment to the charity or yourself, then 14 CFR 91.146 wouldn't apply.
On the other hand, if they are paying the charity for the flight, even if you accept no compensation, the flight is for hire and the rules of 91.146 apply.
If there is any question, the FAA will very likely "connect the dots" between a charitable contribution and the ensuing flight, even if the purpose of the donation wasn't explicitly stated as for the aircraft ride.  They take a very dim view of trying to bypass the regulations like that.

It is my understanding that the issue isn't whether the pilot receives compensation, or anyone else, such as the owner of the plane or the person selling the hamburger.  The issue is that the "passenger is paying something", or giving up something of value, to be in the flight; AND when a passenger is paying for a flight, in the eyes of the FAA, they are due a greater amount of safety guarantee by the FAA.  This is why there is now a min flight hours (500) of a private pilot to fly these flights.
We always tend to think of compensation backwards, as from the pilots perspective.  And we do that because we, the pilots, want to know if "we" are Ok when we carry passengers.  But really the FAA is concerned not so much about us, but for the passengers; and see their (the FAA's) responsibilities toward them, their safety, and their expectations when they have extended value (money, gifts, even good will) for a flight, even if it is just a joy ride or site-seeing trip, or trip to get a hamburger (which is really a trip to go flying of course).
Just imagine a situation, which would likely happen a lot if the FARs allowed, where a freshly minted pilot, with say only 90 hours TT, and all the eagerness in the world to exercise and demonstrate his/her new privilege to everyone who was willing, offered to fly charity flights for his/her church.  Now immagine the likely expectations and assumptions of those that "made a donation" to the church (read paid for) to get a flight.  These people aren't expected to know anything about aviation, pilot certification, annuals, 100 hr checks, or even what makes a plane fly in the first place.  Do you think they are expecting their flight to be piloted by a freshly minted, still scared to stall the plane, pilot?
Looking at it this way makes the FAA's perspective a bit more clear in my mind.  We should always feel a lot more responsible when we are carrying passengers, those that are the sons and daughters, mothers and fathers, friends and loved ones of others.  And we should recognize and honor their expectations when they entrust their lives to fly with us.  We should also understand that if they are unwitting, and in some sense paying passengers of ours, that maybe don't know us and our skills from that of an axe murder, that they likely have at least the expectation that the FAA has their back.

Many people misread 14 CFR 91.146.
The key is to start with (b) which does NOT impose limitations but rather says essentially that "if a bunch of conditions are met" then certain requirements of parts 119 and 120 do not apply.  In other words, IF certain conditions are met then a non-commercial pilot can do the equivalent of 91.147 operations under 91.146.
If, however, those conditions are NOT met, all that "b" means is that the pilot is not relieved from obligations under parts 119 and 120 [generally requiring a commercial pilot's certification and either an LOA for 91.147 or other certification for e.g. part 135 ops].
Depending on whether compensation is provided in a non pro-rata way, the flight may be a private pilot flight as discussed above and subject only to the normal restrictions (common goal amongst all passengers, pro-rata expenses only) or if a commercial pilot is exercising an approved-LOA 91.147 operation.
IF, however, the pilot CHOOSES to meet the extra criteria of b1-b11 and follows (e) then compensation from the charitable event may be received just as it can during 91.147 operations -- and with similar flight restrictions (25sm, nonstop) only with higher pilot qualifications (500hrs) and operational restrictions (FSDO approval and limited number of times a year).
Think of 91.146 as THE ONLY WAY a pilot not holding a commercial certificate can be paid more than the pro-rata share, do the equivalent of a 91.147 flight, but have to have a lot more hours and ops restrictions.


text:
How can dynamic and static pressure be explained?
How exactly do you explain dynamic pressure? If someone asked me what the ASI reads, I would say it reads the dynamic pressure, which is the
ram air pressure (total pressure) - static pressure = dynamic pressure
But would explaining dynamic pressure as "the pressure the pitot tube experiences through the air?
As for static pressure, how would you explain that? Would you say static pressure is the pressure the aircraft feels whether it is in motion or not?

Actually, the ASI reads square root of dynamic pressure (but that's just calibration of the scale, of course).

You are very close. Your explanation of static pressure is correct, but not your dynamic pressure. Ram air pressure is what the pitot tube measures, in other words the total pressure experienced. It is your airspeed gauge which measures dynamic pressure by mechanically (in the case of a traditional pitot-static system) subtracting static pressure from ram air pressure.
If I was explaining this to a layman I would say that ram air pressure is equivalent to sticking your hand out the window of a moving car, while static pressure is the pressure inside the car. That's a bit of an over-simplification as the pressure inside the car will be lower than outside due to the movement through the air, but it gets the point across.

Oops! Thanks @JanHudec.

I get that total pressure minus static pressure gets you dynamic pressure, but how exactly would you explain dynamic pressure. Could you say that dynamic pressure is the pressure the aircraft feels through the air without experiencing the pressure acting on the aircraft?

Actually, in one sense, the Dynamic pressure is not felt by the aircraft at all, as, at each point on the surface of the airframe, the Dynamic pressure is the component which lies parallel to the surface, (it is not pushing on the surface at all). The static pressure is the component that is normal or perpendicular to the surface at each point, and is felt by the aircraft. Of course, the magnitude of the dynamic pressure at each point, (a measure of the indicated airspeed), indirectly tells us how much the static pressure is pushing on the airframe at that point, so ....

Use an energy analogy:

Dynamic pressure equals kinetic energy,
Static pressure equals potential energy.

Total energy = total pressure.

For the more math inclined:

In the gravity field of earth, potential energy is mass times gravity acceleration times height: $E_{pot} = m\cdot g\cdot h$.
Kinetic energy is mass times speed squared, divided by 2: $E_{kin} = m\cdot\frac{v^2}{2}$.
Dynamic pressure $q$ is similarly density times speed squared, divided by 2: $q = \rho\cdot\frac{v^2}{2}$, which makes it a volume-specific kinetic energy.

Static pressure is the weight force of the mass of a column of the atmosphere all the way to space resting on the base area of this column. In other words, the weight of this column of the atmosphere compresses the air lower down so this pressure can support all the air resting on top of it.

If you remember that the air is really a swarm of molecules moving in all directions at very high speed, and that pressure -static or dynamic- is caused by the impact of those molecules, then everything is very clear...

It's simple. Pressure is a force, due to the change in Momentum when a particle bounces off a surface. Because it is a force, it is a vector, (it has a magnitude and a direction), like velocity or acceleration, not a scalar, like temperature or volume, or electric charge.
Secondly, the total pressure must remain constant (principle of conservation of momentum - Newton's third law). So when velocity increases, since the apparent direction of this pressure vector shifts in the direction of the motion, (it appears to align more with the flow motion), the component that is parallel with the motion (dynamic pressure) increases, and the component that is normal or perpendicular to the flow decreases.  The total pressure (magnitude) hasn't changed. Only the components have changed due to a perceptual change in the vector's direction relative to the motion of the observation.
Once you understand this, many things make more sense. A common instrument for measuring Angle of attack these days is a pitot tube with two orifices. One points straight ahead and measures the pressure of the flow vector from that direction. The other is oriented 45 degrees downwards from the forward-oriented orifice and measures the pressure of the airflow vector at that angle. Comparing the two (with appropriate software), allows a computer to calculate the Angle of Attack.


text:
How should a loss of communications in VFR be dealt with?
Let's say I'm flying a cross country flight and I wanted to land in a Class D or enter Class C towered airport, but I lost my two-way communications radio but have my transponder squawking 7600. Should I blindly continue in and receive light gun signals to land or should I steer out the Class C and D and divert to a non-towered airport? In worst case scenario, what if my transponder is also out?

should I blindly continue in

First, never do anything "blindly".
The FAR and the AIM address the Class D question, so this part is the most easily answerable:

FAR 91.129 (d) Communications failure. Each person who operates an aircraft in a Class D airspace area must maintain two-way radio communications with the ATC facility having jurisdiction over that area.
(1) If the aircraft radio fails in flight under IFR, the pilot must comply with §91.185 of the part.
(2) If the aircraft radio fails in flight under VFR, the pilot in command may operate that aircraft and land if—
(i) Weather conditions are at or above basic VFR weather minimums;
(ii) Visual contact with the tower is maintained; and
(iii) A clearance to land is received.
AIM 4-2-13 (3). Transmitter and receiver inoperative. Remain outside or above the Class D surface area until the direction and flow of traffic has been determined; then, join the airport traffic pattern and maintain visual  contact with the tower to receive light signals. Acknowledge light signals as noted above.

After that, 6−4−1 addresses more two-way comms failure actions:

a. It is virtually impossible to provide regulations and procedures
  applicable to all possible situations associated with two-way radio
  communications failure. During two-way radio communications failure,
  when confronted by a situation not covered in the regulation, pilots
  are expected to exercise good judgment in whatever action they elect
  to take. Should the situation so dictate they should not be reluctant
  to use the emergency action contained in 14 CFR Section 91.3(b).

Since "best judgement" is very situational dependent, the rest of this is subjective:  I would not enter Class C, if there was another alternative. If you're already in Class C, and there are Class D/E/G airports available, divert. If you're already in Class C,and there are no other options, continue with the utmost caution (following the advice of the Class D procedures if able), using your own light signals to attempt to alert the tower.

Some "armchair lawyers" might even say that lost-comms (VFR) operations in Class C and even Class B could be conducted in the same manner as Class D, because each section starts with: "each aircraft operation in Class B/C airspace must be conducted in compliance with this section and 91.129."
I'd personally avoid B and C like the plague if I was VFR lost comms.

But isn't it so that if you have a flight plan, ATC will expect you to stick to it and therefore you should (and thus not divert)?

The OP asked with reference to VFR flight (not the conditions, or weather, but the rules themselves).  There is no technical requirement for a VFR flight to file a flight plan, and even if one was filed with Flight Service, ATC is not involved and is not tracking the flight. Therefore, there is nothing that ATC is expecting the flight to "stick to".

@Jimmy 100% Agree, ATC don't always keep track of VFR flight plans until they are needed. Everyday I have a pile of VFR flight plans that are never needed as they never called up. Flight Service knew about them not me.

Even with an activated VFR flight plan, if you were not on flight following then you just show up as another 1200 and they really can't know which 1200 is which flight plan. Squawking 7600 is better in that they know this radar dot has lost radio but again it started as just another 1200 and they don't know which.


text:
Are 'climb via a SID' instructions actually used in the US?
In the USA, a departing aircraft is instructed to climb:

to flight level and maintain, or
via standard instrument departure (SID)

That's according to US Aeronautical Information Publication (AIP). But pilots say they never hear climb via SID. Can anybody clarify if climb via SID instruction is really used by ATC?

In my experience, I've received a climb via SID many times at airports like Las Vegas and Teterboro.
This is common at certain airports, but a lot of airports don't use it because the procedures aren't designed that way.
I think that a lot of pilots, especially those flying smaller non-turbine powered aircraft, don't receive this type of clearance because:

They are flying at smaller airports that don't have a SID which uses it, or
They are not assigned the SID's which do have it because the SID is only assigned to turbine-powered aircraft or aircraft capable of flight above a certain speed or altitude.

It is also a relatively new procedure in the US.  They were originally going to start using it in 2014, but it got delayed and was finally implemented a year or two ago (I don't remember exactly when).  For a while, the US was only using "descend via" clearances, and not "climb via" clearances.
Here are a couple of resources about this:

NBAA PBN site
FAA Climb Via/Descend Via Speed Clearances
Frequently Asked Questions
FAA “Climb Via” and “Descend Via” Procedures and Phraseology Air Traffic Policy Notice

What's the reason the "climb via" procedure has been newly introduced recently? Is it just to further reduce the workloads of ATCs and pilots?

@lemonincider -- that should be its own question :)

Every IFR departure I've heard at KRNT has involved "..., climb via the SID, expect ..."

Thanks for the answer. I've read in the US AIP that climb via/ descend via are the phrases the pilots must be prepared to get from ATC but my fellow pilots who fly to the USA say they don't get such instructions. Perhaps it's not because this phraseology does not exist in general but maybe it is more convenient for controllers to use 'climb and maintain' instruction and ATC people prefer 'climb and maintain'  to 'climb via SID'? If a controller does say 'climb via SID' is it pronounced 'sid' or 's-i-d'?

@Delmar It's probably more that the procedures in use at the airports that your friends visit have not been designed with a climb via instruction. Because it's relatively new, if they even want to use it at a particular airport, they would need to be redesigned and that takes time to do everywhere. As far as pronunciation, the clearance pronounces it 'sid', and when the pilot contacts departure control, they use the procedure name instead of saying sid, like 'Climbing Via the Teterboro 2 departure.'

@lemonincider I'm not 100% sure why, but originally they introduced climb via and descend via clearances at the same time.  I'm guessing that there was too much confusion so they decided to scale back and only do one at a time.


text:
What's the difference between a TSO Authorization and a letter of TSO design approval?
FAA can issue two types of approval for a TSO part application: TSO Authorization and letter of TSO design approval. What's the difference?
Does it relate to the approval being design-only or production only?
Also, do other Airworthiness Authorities have a similar difference?
According to 14 CFR 21 Subpart O §21.601:

(2) A TSO authorization is an FAA design and production approval
  issued to the manufacturer of an article that has been found to meet a
  specific TSO;
(3) A letter of TSO design approval is an FAA design approval for an
  article that has been found to meet a specific TSO in accordance with
  the procedures of § 21.621;
(4) An article manufactured under a TSO authorization, an FAA letter
  of acceptance as described in § 21.613(b), or an article manufactured
  under a letter of TSO design approval described in § 21.621 is an
  approved article for the purpose of meeting the regulations of this
  chapter that require the article to be approved;

I don't know much about this, but it looks like a TSO Authorization is for domestic (US) manufacturers, and a letter of TSO design approval is for foreign manufacturers who want to import their products into the US. See 21.621:

§21.621   Issue of letters of TSO design approval: Import articles.
(a) The FAA may issue a letter of TSO design approval for an article—
(1) Designed and manufactured in a foreign country or jurisdiction
  subject to the export provisions of an agreement with the United
  States for the acceptance of these articles for import; and
(2) For import into the United States if— [...]

And the FAA's page on it says:

What is a letter of design approval?
  An FAA design approval for an article manufactured outside the United States that meets a
  specific TSO.

I have no idea about other aviation authorities, but I assume there are similar regulations in other countries because the same general issue exists everywhere: how do you ensure that both manufactured and imported aviation components meet all required standards?

As for your last question, dealing with imported parts is quite a tough problem as it depends on specific agreements between countries. See https://www.easa.europa.eu/document-library/international-cooperation-overview


text:
Is there a dedicated emergency frequency?
Coast patrol has a dedicated frequency for emergency that must be watched at almost all hours, and even if I recall, it had a "dead silent period" to prioritise whatever emergency might be reported. Is there a dedicated frequency for aviation? Or shall MAYDAYs just be sent to the standard ATC frequency?

Assuming you are talking about verbal communications this is the best answer below. However, as far as emergency frequencies in general there are others such as 406.0-406.1mhz that is used for Emergency Locator Transmitters. They give a specific identification code assigned by NOAA that can be picked up by satellite to aid in both crash identification as well as search and rescue effort.

If a pilot is already speaking to ATC (or monitoring a frequency) they should continue to use that frequency for any emergency or abnormal situation.
If they are not currently receiving ATC services or on an ATC frequency, attempt to use 121.5. Many ATC providers and enroute airliners monitor this frequency and can relay or provide assistance.
The FAA's AIM (6-3-1) describes emergency use of 121.5 in the United States:

h. Although the frequency in use or other frequencies assigned by ATC are preferable, the following emergency frequencies can be used for distress or urgency communications, if necessary or desirable:

1. 121.5 MHz and 243.0 MHz. Both have a range generally limited to line of sight. 121.5 MHz is guarded by direction finding stations and some military and civil aircraft. 243.0 MHz is guarded by military aircraft. Both 121.5 MHz and 243.0 MHz are guarded by military towers, most civil towers, FSSs, and radar facilities. Normally ARTCC emergency frequency capability does not extend to radar coverage limits. [emphasis mine] If an ARTCC does not respond when called on 121.5 MHz or 243.0 MHz, call the nearest tower or FSS.

And if you're far enough from the nearest ARTCC to be communicating using HF, the guard frequency to try is 2.182 MHz.

Yes, the aircraft emergency frequency (which we often call "guard") is 121.5 MHz.
This is monitored by many control towers and flight service stations. It is also typically monitored by airplanes on cross-country trips (especially airliners). You will occasionally hear ATC ask an airplane to try to contact another airplane "on guard" in an attempt to relay a message to an aircraft which they have lost communications with.
However, if you are currently in communication with ATC on another frequency, or there is a frequency where you know you can communicate your distress and it will be heard, you should use that frequency instead, because there is no guarantee your message will be heard on 121.5 in all parts of the country/world.
Older ELT's (emergency locator transmitter) also transmitted a siren type sound on this frequency when activated which sounds like this.
In addition, it is used as an intercept frequency. In other words, if you get intercepted by a fighter jet, you better be listening in on 121.5 for any commands they give you.

ATC would most probably ask other aircraft to relay messages to a not responding aircraft on the current frequency, as both aircraft are supposed to be monitoring this. Guard is only rarely used for this purpose and not mend to. These messages commonly includes the instruction for the 'lost' (not talkin about navigation) to check in on another frequency as they are outside the line of sight (VHF communication) or range of the receiver transmitter for this ATC frequency.

@Falk that's true, and the more common situation. I said occasionally because I have heard it happen occasionally.

No worries, I just like to add this because guard is already 'abused' far too often and I like to avoid this as far as possible. Everything I receive on guard is getting all my capacity I don't need to actually fly the aircraft. If the transmitting station may be some further away, parts of a simple chat could sound like an emergency call and I'm probably not the only one who's then carefully monitoring .5 and maybe forgetting about something he was about to do (some nearly worst case - actually worst case would be hearing an emergency call and thinking it's one of these abuses of guard)

@Harv that's a separate question. If you'd like to ask it on the site, please feel free.

Unless you fly well enough to evade a fighter jet (not difficult).

@Cloud I'm not sure your average airliner is agile enough to avoid a fighter jet, I don't think they're sending a fighter jet against slower planes (those prove less of a risk and AFAIK fly slower than the stall speed of most fighter jets), and generally it's not the fighter jet but their missiles you need to be wary of.

As a general rule, declaring an emergency should be done on the frequency you are currently communicating on. However, there is a dedicated emergency frequency as Bret said (121.5 MHz), which is the same all over the world. It's generally used if there is no response from the ATC facility the pilot was communicating with.
On many glass cockpits there's even a shortcut to tune to the emergency frequency. For example, on Garmin equipment like the G1000 and G530/430 you have to press and hold the "flip-flop" key for 2 seconds and it will automatically tune 121.5 for you.

Canada has similar procedures to the US.  From the Transport Canada Aeronautical Information Manual, in the COM section:

5.11 Emergency Communications
[...]
The first transmission of the distress call and message by an aircraft
  should be on the air-to-ground frequency in use at the time. If the
  aircraft is unable to establish communication on the frequency in use,
  the distress call and message should be repeated on the HF general
  calling or distress frequency 3 023.5 kHz, 5 680 kHz, 121.5 MHz, 406.1
  MHz, or other distress frequency available, such as 2 182 kHz, in an
  effort to establish communications with any ground station or the
  maritime service.

If you have two radios it is a good idea to monitor 121.5 on your second radio.  You can set the volume slightly lower than the primary radio you are listening to.
Doing this allows you to hear ELT's (remember the old ELT's are not monitored by satellites anymore - just the 406 elt's)  So if you hear an ELT you can notify ATC and they can investigate it.  This has helped more than one downed pilot.
Also, if you are flying VFR and nearing a TFR, or other restricted airspace, you may get a call in the blind on 121.5 giving your position, direction of flight, and altitude readout along with a warning that you are about to enter, or have entered restricted airspace.  This call may keep you from having a violation.
If you are in the restricted airspace, the call will include a direction to exit the airspace and usually a frequency to contact for directions.
We all need to help and watch out for each other.  If you do this long enough you will make a call on 121.5 in error.  At that time all of the people who never make mistakes will point it out to you.  Just remember, by monitoring 121.5 you can keep yourself stay out of trouble and help someone else who has experienced trouble.

121.5 MHz is the international civilian distress frequency. It has been designated for emergency communication by an international agreement.
ICAO Annex 10, Volume V, § 4.1.3.1.1 states that frequency 121.5 MHz “shall be used only for genuine emergency purposes” broadly covering the following activities:

The handling of an emergency situations;
air-ground communication with aircraft with airborne equipment failure;
search and rescue operations and the operation of emergency locator transmitters (ELTs); and
air policing/interception action.


text:
Has the FAA ever granted anybody a license honoris causa?
Say, anybody who made an outstanding contribution to technology, flight methodologies, etc (for example, the Wright Brothers); has the FAA ever issued a license (private pilot, etc.) to anyone that deserved such honor?

I suspect the answer is no, but I have no evidence.

My inclination is to say no -- certainly not in "modern times", as issuing an airman/mechanic/ATC certificate to someone without the relevant training would be a Bad Thing. It's possible that in the early days (back when the FAA was still the CAA - Civil Aviation Administration) pilots who had been flying before the administration was established were "grandfathered" and given licenses - It's certainly an interesting research question.

I don't think the FAA considers licenses to be an "Honor", the same way that Universities consider a Degree to be an "Honor".  A license is strictly an license; an authorizing document, stating that the holder has met certain training requirements.

A license granted honoris causa is an honor, same with degrees, @abelenky

It's an interesting question, and according to AOPA they did award one to the guy who designed the current FAA license card:

The FAA awarded Dahlvang his own (honorary) certificate, nicely framed
  with a gold seal.

But it doesn't say what's printed on that certificate and I assume it isn't actually valid for flight. If you give someone a real pilot's license you give them the authority to operate an aircraft and I can't imagine the FAA handing out licenses to unqualified people.
Orville Wright did get an honorary certificate, as did other 'old-timers', but that pre-dates the FAA and again it isn't clear if they were 'real' certificates or not:

Orville Wright
Evan J. Parker

I don't know if that really answers the question, but anyway in practical terms I think it's probably a lot easier for the FAA to come up with a suitably impressive but legally worthless certificate rather than give someone a real one and deal with the legal issues involved in breaking their own rules and possibly federal law.

I could have designed a better license. However, good answer.

A little digging on the airman registry didn't turn up a certificate for Mr. Dahlvang, but some poking around on the artist's own site turned up this -- so basically just a print run with no aviation privileges :)

I could use an FAA-approved "graphic designer" license... By the way it still looks too legit and you could easily fool many people into thinking you are actually qualified to be a pilot. Heh.

@ppp can't you get a student pilot certificate with no qualifications?


text:
Who's in charge of running VOLMET stations worldwide?
Are the broadcasters private individuals, governments, companies? Are they required to function 24/7 and if they don't, are the owners fined?

This is an interesting question. According to the Air Navigation Plan of the ICAO (Part 6), all member countries have to broadcast these volmets, therefore it is extremely likely, that all Volmet stations are run by the government.
It also states that this service has to be available all the time, but I doubt that fines are involved. There will be a Notam issued though.
Source: http://aviadocs.net/icaodocs/Docs/9673_vol1_en.pdf

Most countries have surely delegated the responsibility for VOLMETs to the local ANSP(s).


text:
Would a "fuel leak" at the gate be a reportable incident?
This news story shows video of fuel being expelled from a wingtip of a 767, while at the gate. The engines were apparently running during this event. After the cockpit crew learned of what was going on, the engines were shut down and fire equipment was brought in.
Since this happened on the ground, is this an incident that must be reported to the FAA? The article says that the airline hasn't given any details of the incident.
Perhaps this belongs in another question, but what could have happened here?

It looks like somebody hit the fuel-discharge switch, which would be surprising since I believe that the discharge system is a set of guarded switches. It may also be that the fueling system vents are at the same place and somebody overfilled the tanks.

Yes, this really should be two questions.  One about the reporting requirements, and one about a possible explanation.  I didn't even notice the second question until I was done writing my answer!

There are a couple of places in the regualtions that require FAA or NTSB notification of certain events:

14 CFR 121.703 Service difficulty reports
14 CFR 121.705 Mechanical interruption summary report
49 CFR 830.5 Immediate notification (to the NTSB)

The closest thing to what you described would be the following in 121.703(a):

(11) A fuel or fuel-dumping system that affects fuel flow or causes hazardous leakage during flight;

Note that it says during flight though, so this wouldn't apply and they wouldn't be required to report it.